Last seen for £829 at Silentnight on 2nd September 2026
Silentnight Just Sleep Calm Super King Mattress
The Silentnight Just Sleep Calm sits within Silentnight's Just Sleep range, available in UK Single, UK Double and UK Super King.
- Medium-firm feel for most sleepers
- Fabric surface absorbs body heat
- Support right up to the edges
Save with the previous model
Some retailers still sell the earlier version of this mattress for less than the current model's best price.
More available sizes
Last seen for £829 at Silentnight on 2nd September 2026
Last seen for £619 at Silentnight on 2nd September 2026
Last seen for £735 at Silentnight on 24th June 2026
Last seen for £669 at Silentnight on 2nd September 2026
Mattress details
Mattress
Silentnight Just Sleep Calm Mattress
Size
Firmness
Medium Firm
Construction
Depth (cm)
Layers
Layer Details
Key benefits
- Real separation from a restless partner: With 90cm each for two people sharing, a fidgeting or early-rising partner is simply further away, which does more for your sleep than most upgrades.
- Space when the family piles in: If children wander in during the night, or a large dog treats the bed as home, 180cm of width means everyone still gets a genuine share.
- Fills a large master properly: In a period bedroom or a generous new build master, a UK king can look lost against the wall; the extra 30cm of the super king sits in proportion.
- Extra length for taller sleepers: At 200cm long, that's 6ft 6in, it gives anyone approaching six foot clear space without feet hanging over the end.
- The largest standard UK size: At 6ft x 6ft 6in this is as much sleeping space as mainstream UK sizes go, so you're never left wondering if you should have gone bigger.
This size suits you if...
You share every night and want enough width that a restless partner, a wandering child or a pet on the covers doesn't cost you sleep, or your bedroom is large enough that a UK king would look undersized. We'd suggest allowing at least 3m x 2.9m of floor space, with room left for wardrobe doors to open and a clear walkway on both sides.
Consider another size if...
Your bedroom is under our suggested 3m x 2.9m minimum, or you'd struggle to get a 180cm-wide mattress round the turns of your landing. We'd recommend the UK double instead, which is 45cm narrower and needs around 2.6m x 2.8m.
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FAQ's
How big is the Silentnight Just Sleep Calm in a UK super king?
It measures 180 x 200cm, which is 6ft x 6ft 6in. For two people sharing, that works out at 90cm each, about the width of a single bed apiece, which is why this size suits couples where one partner moves around a lot at night.
What room size do I need for the Silentnight Just Sleep Calm super king?
We suggest allowing at least 3m x 2.9m. That leaves space to walk down both sides and open drawers or wardrobe doors without shuffling sideways. In a loft conversion, check the ceiling slope too, since a bed this wide limits which wall it can sit against.
Should I choose the super king or the UK king for this mattress?
The UK super king is 30cm wider than the UK king, and both are the same 200cm length, so the decision is purely about width and room size. If children or pets regularly join you, the extra width is the difference between comfortable and cramped. For the UK king we suggest at least 2.7m x 2.9m.
How much bigger is the super king than the double?
The UK super king is 45cm wider and 10cm longer than the UK double. That's a substantial jump: nearly half a metre of extra width across the bed, plus added legroom for taller sleepers. The bedding steps up too, so budget for super king sheets and a larger duvet.
Is the Silentnight Just Sleep Calm super king a good choice for families?
Size-wise, yes. At 180cm wide there's room for a child who wanders in at 3am without anyone ending up on the edge. Silentnight doesn't publish full construction or firmness details for this model, though, so check the retailer's listing before buying if support for different weights matters to you.